Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.88	3.672%	$218.6235	$218.62	$218.60	$218.60
Purchase #2	$75.42	4.625%	$78.9082	$78.91	$78.90	$78.90
Purchase #3	$97.56	12.462%	$109.7179	$109.72	$109.70	$109.70
Purchase #4	$187.38	9.716%	$205.5858	$205.59	$205.60	$205.60
Purchase #5	$188.81	11.112%	$209.7906	$209.79	$209.80	$209.80
Purchase #6	$167.83	5.199%	$176.5555	$176.56	$176.55	$176.60
Purchase #7	$41.58	5.383%	$43.8183	$43.82	$43.80	$43.80
7 purchase totals =	$969.46		$1,042.9998	$1,043.01	$1,042.95	$1,043.00